This BIOMASS Theme 2 report has been produced by the Remediation Working Group, which is concerned with the evaluation of the reliability of dose and risk assessment methodologies applied in support of decisions related to the cost-effectiveness of risk reduction measures within an environmental remediation programme. Scenarios have been developed concerning the site contaminated by an old radium extraction plant in Olen (Belgium) in order to test biosphere models. Two possible remedial actions were considered, namely the removal of surface soil in the most contaminated areas and the covering with a clean soil layer. The aim of the scenario was to assess the possible influence of these remediation measures on the radiological impact to the local population. Six models participated in the intercomparison modelling exercise. Deterministic and stochastic calculations were made, whereby the parameters considered in the uncertainty analysis were selected by the modellers. Example of doses calculation is presented made by the CLRP_RAD spreadsheet model that has been specially designed for the BIOMASS Theme 2 Scenario Olen-B exercise. Stochastic calculation was performed using commercially available stochastic package Crystal Ball 2000 that enables user to use electronic spreadsheet model. The uncertainty analysis has been performed for the endpoints specified in Scenario. Looking at the total dose predictions, one can concluded that based on the generic criterion, cleanup actions are not likely needed. However, as shown earlier, the radon indoors is the main exposure pathway. This implies according to the ICRP statement that actions to reduce the radon indoors might still be justifiable.
What is the BIOMASS Programme?
BIOMASS (Biosphere Modelling and Assessment Methods) is the fourth in a series of international programs aimed at the improvement of methods for assessing the impact of radionuclides in the environment; the first three were the VAMP program, sponsored by the International Atomic Energy Agency (IAEA), and BIOMOVS (BIOspheric MOdel Validation Study) Phases I and II, supported by organisations from Canada, Spain and Sweden. These programs have served to provide forums to promote international collaboration, information exchange, and peer review in the area of modelling and assessment of the movement of radionuclides and other pollutants in the environment.
The scope of the BIOMASS program is the scientific, experimental, and technical aspects related to the analysis and assessment of the behaviour of radionuclides in the environment and their associated impacts. Special emphasis is being placed on the improvement of the accuracy of model predictions, on the improvement of modelling techniques, and on the promotion of experimental activities and field data gathering to complement assessments.
Three important areas involving environmental assessment modelling are being covered: Theme 1, Radioactive waste disposal (emphasis on reference biospheres); Theme 2, Environmental Releases (including remediation of areas contaminated as a result of nuclear accidents, unrestricted releases or poor management practices, and reconstruction of radiation doses received due to accidental or poorly controlled releases); and Theme 3, Biosphere Processes (current emphases on tritium fruit trees, and forests).